Jim Holden and the crew of the Rocinante are part of a vast flotilla of scientific and military ships going out to examine the artifact. But behind the scenes, a complex plot is unfolding, with the destruction of Holden at its core. As the emissaries of the human race try to find whether the gate is an opportunity or a threat, the greatest danger is the one they brought with them.

A "slingshotter" takes his ship, the Y Que, through the Ring, an artificial stable wormhole created by Venus, in orbit beyond Uranus; it decelerates at 99 g and his body is splattered inside the ship, but the ship doesn't come out the other side of the Ring. A live feed from the Y Que broadcasts the events.

The Roci crew has had a prosperous year; they've made a bunch of ship upgrades including joining Naomi and Holden's rooms and adding a railgun. Detective Miller continues to visit Holden, but he doesn't seem to actually hear Holden or talk directly to him; he mostly seems to speak gibberish. He asks Holden for help and says "they know I find things. They know you help me." Naomi knows about it, but Holden hasn't told the others.

There's a food shortage for the outer planets and the Asteroid Belt, since Ganymede now produces less than 1/4 of its previous food output. Venus is completely dead. Inside the Ring is some sort of anomaly.

Bull (Carlos c de Baca) is a former UN marine, now member of the OPA and XO on the Behemoth, the largest weapons ship in the Sol system. Formerly, it was known as the Nauvoo, but commandeered by Fred Johnson during the Eros incident. The Behemoth is considered a "retrofitted piece of crap" that wouldn't hold up in a real fight; it's mainly for show. Just before launch, Bull is re-assigned to chief security officer; Captain Ashford doesn't want a former Earther as second in command of the OPA's flagship.

Clarissa Mao, daughter of Jules-Pierre Mao, gets a new identity as Melba Koh and will soon be shipping out on the Cerisier, a civilian maintenance ship going to the Ring. The guy selling her the new identity tries to shake her down and she kills him and his goons. She plans to humiliate James Holden for destroying her family, then kill him.

Europan Pastor Annushka Volovodov has been chosen for the Secretary-General's advisory group for the civilian trip to the Ring. She boards the UNN Thomas Prince, a Xerxes-class battleship.

If the Nauvoo fires its railgun, the ship will be torn apart. Many of its parts were built to spin, since the ship would have thrust gravity only at the start and end of its journey. Bull can't get the budget from the XO, Michio Pa, to fix many of the problems. Samara Rosenberg from Tycho is the chief engineer.

Holden takes a job as far away from the Ring as possible, but the employer backs out at the last minute when Holden is served a summons from Mars; they want the Roci back, and it's impounded at Ceres. Monica Stuart from UN Public Broadcasting wants to do a story on the Ring, and asks Holden to take her and her team there; under the Freedom of Journalism Act, she has reasonable use of any hired materials and personnel. Holden believes Miller might be behind all of this.

Melba commands a team of 4 technicians on the Cerisier, but she's doing a poor job of faking it. She leaves a bomb on a ship called the Seung Un; she creates a video of Holden saying he's claiming control of the Ring on behalf of the OPA, and has paid someone on Ceres to setup a remote connection on the Roci. She confides in Ren, a member of her team, that she's in over her head with the engineering job, and he says he'll help her out.

The Behemoth staff have been showing up to work high. Bull (with his deputy Serge), bust a drug dealer and Bull nonchalantly puts him out an airlock. Ashford relieves him of duty, but Bull explains that on a military vessel anyone endangering the ship is to be executed. Ashford waffles and tells him never to do it again. The XO recognizes that Bull did this to show the crew he's more Belter than the captain, and he just made her shit list.

Miller keeps telling Holden to check his doors and corners and to clear the room or he's going to wind up dead; Holden's not so sure he's just speaking gibberish any more. Data shows that the Y Que is still moving in a straight line at a constant velocity of 600 m/s.

Ren confronts Melba after he gets air filter data from the Seung Un indicating there might be a bomb aboard; she turns into a ninja, breaks his neck, then seals his corpse up in a storage locker in her room.

Anna starts holding prayer meetings on the Prince, as many of the crew are distraught about the Ring. She sees a young woman that looks like she needs help; it's Melba, and she's going crazy with remorse after killing Ren. She thinks Anna somehow knows what she did, and tweaks out at her.

Melba heads back to the Cerisier and activates the software on the Roci, issuing a trigger code to blow up the Seung Un, announcing Holden's responsibility and demands, then powering up weapons and targeting systems.

On the Behemoth, probes sent into the wormhole have determined there are a number of large objects, possibly ships, on the other side. XO Pa revokes Sam's access privileges for making repairs Bull told her to do; Pa knows this, but is politicking to turn Bull's allies against him.

Bull gets the transmission from Holden demanding that the information and resources about the Ring remain free to all people and that he'll kill anyone who tries to stop him. Bull and Pa tell Ashford to shoot down the Roci so Earth doesn't think the OPA is on his side; Ashford reluctantly fires a torpedo, but this causes the whole ship to lose power. The XO lets Sam out of confinement to fix the ship.

Holden realizes the lawsuit and the camera crew were a setup for this moment. The Behemoth fires a torpedo at them, but Naomi's countermeasures are all offline. With no other options, they take the Roci into the Ring.

Ashford wants to follow the Roci through Ring; Mars vows to destroy them if they even get close to the Ring. Bull suggests to Pa that they overthrow the captain, but she insists they follow the chain of command.

Hector "Hank" Cortez, spiritual advisor to the UN Secretary-General, asks Anna to sign a petition to take the Prince into the Ring; she immediately agrees, seeing it as a way to reunite the fleets and stave off war.

Melba is extremely upset that Holden survived her sabotage. When the Cersier's employers order a number of crew to be dispatched to the Prince to chase after Holden, she volunteers. Before leaving, she removes Ren from her storage locker and stores him in her tool chest. On the Prince, she recognizes Anna's friend Tilly, who used to babysit her.

The inside of the Ring is 1,000,000 km across, bounded by 1,373 wormholes spaced into a sphere. The only open Ring is the one to Earth’s system, Sol. In the center is the Ring Station, a metal sphere five kilometers across. Orbiting it are the Y Que and the probes that have been sent through. In the "Slow Zone", as it was nicknamed, nothing can go faster than 600 m/s.

Amos is replacing a lightbulb in the head, when he finds the transmitter that was hacking their system. One of the documentary crew, a blind guy, admits that he got paid to stick it there. His glasses have a sonar optic system that he uses to create a 3D model of the woman who paid him; Holden thinks it's Julie Mao.

Naomi puts out a broadcast saying the previous message was a fake; the other ships demand to see Holden, but he's EVA en route to the sphere. Bull tells Naomi that Ashford wants to send in an attack squad, and that he'll take the civilians off her hands.

The sphere's irises open and lets Holden enter. Inside, Miller explains that he's not actually there in person; he's the "machine for finding lost things" and can interface with the sphere's systems.

Martian marines in exosuits catch up with Holden. An insect-like alien defense robot attempts to stop them, but they destroy it with a grenade; this teaches the station that even things moving as fast as a baseball pitch are dangerous, and the Slow Zone slows down even more, causing massive casualties on all the ships. More alien defensive mechanisms activate and begin ripping the marines to pieces; they fall back.

Melba uses the deceleration catastrophe to steal a mech suit and EVA to the Roci. She breaks in through the cargo door and attacks Naomi in engineering. Naomi’s shoulder is crushed by the mech, and just as Melba is about to break her neck, Anna tazes her. Anna had recognized Melba in Naomi's broadcast as the girl who freaked out at her and pieced things together when Tilly told her that the image was of Claire Mao. Anna, high on amphetamines due to having been injured during deceleration, stole a tazer and an EVA suit and followed Melba.

Melba starts to recover, so Naomi and Anna flee; Melba keeps ripping all the doors open with her mech suit. Naomi passes out from blood loss. Anna grabs her and they hide in a locker. Melba begins tearing the locker doors off, but her mech's battery runs out. She uses her glands and starts kicking and ripping the locker door off with her bare hands, but the effects wear off before she can get to them. Anna sedates her and tapes her to a chair.

Holden asks Miller to tell the station to help the people on the ships; Miller says it's utilitarian and can't do anything like that. Miller takes him to the central core; he needs Holden to physically touch the interface in order to authorize Miller for remote access to it, since Miller himself is actually just the protomolecule running "the most complex simulation in the history of [the] solar system" inside Holden's brain to make it seem like he's there with him.

When Holden touches the core, his consciousness ascends and he learns about the creators, who were a galaxy-spanning hive consciousness; he can sense entire star systems with his mind. He realizes the creators were sending fire through the Rings and blowing up entire star systems to try and quarantine something from coming through. The station has been waiting two billion years for the all-clear to re-open the wormhole network. Miller says the station is in "war mode.” Martians show up and take Holden away.

Bull awakes in the medical bay, paralyzed from the waist down. The doctor insists on putting him in a medical coma, but Bull has too much work to do; the injured people on all the ships won't heal properly in zero-g, so he wants to spin up the Behemoth's drum to create gravity. Sam has to remove the railgun and torpedo tubes first, and when Ashford finds out Bull has orchestrated this, he goes crazy with rage and orders Bull into the coma. Pa and Bull relieve him of duty, making Pa the captain. Bull contacts the Roci and Anna tells him she thinks Melba blew up the Seung Un, and that they need help.

Holden is taken to the MCRN Hammurabi where he explains everything that has happened so far. He's put in a holding cell; Miller appears and tells him they all need to shut down their ship's power so he can unspring the lockdown. This will probably open up all the Rings, which could be very bad, but Miller needs to know what happened.

Melba is locked up on the Behemoth; she's near catatonic. Ashford is in a cell beside her and promises her amnesty if she helps get him out; she ignores him. She won't respond to Bull, so he sends in Tilly; she confesses that she did it all because Holden "hurt daddy."

Anna and the Roci crew are taken to the Behemoth. Tilly asks Anna to speak with Claire; she again confesses everything, but Anna wants to redeem her. Claire says there's no justice in that and doesn't want forgiveness for the terrible things she's done.

Bull gets a call from Captain Jakande on the Hammurabi; she won't come to the Behemoth or give up Holden, because the MCRN won't let her surrender. Sam gifts Bull a modified mech suit that lets him walk; he's deeply touched. Bull asks her to turn the comm laser into a weapon so he can give the Martians a reason to surrender; they surrender willingly, and Holden is en route.

When Holden arrives, he tells Pa everything, including how to shut off the protomolecule's hold on them. He heads to the medical bay to check on his crew and he's accosted by Anna. She tells him about Claire, then takes him to see his crew, who are all grateful to her for saving their lives. Anna asks them to forgive Clarissa, and Holden reluctantly agrees when Naomi says she forgives her.

Clarissa regains conscientiousness and is taken to hating herself instead of Holden. She eavesdrops on Ashford's visitors and realizes they're planning a coup. Hector Cortez, who used to golf with her father, asks her to join the coup; he feels responsible for many of the deaths, since he was the one who petitioned to come into the Ring. He's joined with Ashford so they can use the comm laser to destroy the gate – locking themselves inside – in order to stop others from following them. He wants Claire to use her abilities to keep Ashford alive. Deciding that all the deaths will be given meaning this way, she agrees.

Bull gets a call from Serge warning that Ashford's people are taking over. Bull warns Pa, then calls Sam; she tells him Ashford's guys took engineering and asked her to overclock the laser, so they can destroy the Ring. She tells him to hole up in one of the storage lockers and he does. Serge is killed in a skirmish with Ashford's soldiers.

Cortez asks Anna for her help controlling the mob after they close the Ring; she disagrees that that is the solution, and refuses to join him.

The Roci crew realizes something is going down; Naomi calls Sam, who tells them to hide and that she'll join them shortly. While en route, they beat up a couple of insurgents and take their weapons. They rendezvous with Sam and she fills them in, explaining that using the laser will melt that entire side of the ship; Holden tells her that if they attack, the Ring Station might destroy their entire solar system. Sam sends them to find Bull while she sabotages the laser. Bull rounds up his people and they set up base in the admin offices where Radio Free Slow Zone has been broadcasting from. Bull has the journalist Monica and preacher Anna do a broadcast explaining the situation and asking everyone to shut down their reactors so the station will let the ships go.

Sam continues to sabotage the laser; Ashford calls her to the bridge and when another engineer disagrees with how long the repairs should take, he shoots Sam. With Sam dead, Naomi is tasked with shutting down the reactor and gassing the bridge; Holden will take the bridge once they're all unconscious; Amos will stay and guard Anna; and Alex will head back to the Roci to secure it.

Bull's team retakes engineering. Naomi tries to gas the bridge, but Clarissa disables remote access to it. Ashford sends out a team of four soldiers equipped with confiscated Martian power armor. He shut downs the rotating drum section of the Behemoth – leading to another catastrophic inertia change and injuring even more people – and sends the armored soldiers straight through to engineering.

Bull, Naomi, et. al. are forced to retreat from engineering when the four power-suited soldiers arrive. Naomi managed to dump the core, but not the grid, thus Ashford can still fire the laser. They escape out an airlock and into an elevator shaft in vacuum. Juarez, the martian sniper, manages to take out one of the mechs. Bull stays behind to cover them; he throws his two remaining grenades at the pursuing mech warriors, killing one of them and sacrificing himself.

In the offices, Amos manages to repel the attack, but his team suffers massive casualties. Anna broadcasts that they're losing the fight and that they need to stop Ashford or Earth will be destroyed. Clarissa calls and says she could open the bridge doors for Holden, but wants Anna to convince her; Anna says to have faith in the people who chose to forgive her in spite of the pain she's caused them, and to stop siding with Ashford, who kills innocents out of convenience. Clarissa opens the doors.

Naomi rigs the backup elevator to engage, squashing the two remaining marines in mech armor like bugs. The hatch opens and fire is exchanged from both sides. Ashford tries to shoot Claire, but she dropkicks him, then re-rigs the bridge access controls, allowing the grid to be taken offline. The ship shuts down and the lights go out.

Holden suddenly finds himself on an alien planet with proto-Miller. With all the ships powered down, Miller managed to shut down the station's defenses, which freed the ships and opened all the Rings. No malevolent force appears and kills them, but Miller warns him that they could still be out there. Even though his creators are gone, Miller can't stop searching for them and tells Holden he "needs a ride."

Anna insists that Clarissa gets a fair trial on Luna, and asks Holden to transport her there. When he refuses, she offers to buy the Roci from Mars and give it to him if he'll agree; she calls up Tilly and asks her to foot the bill, and she will. Aboard the Roci, Claire helps Amos fix all the damage she caused, and finds she really enjoys the crew's company.

The title refers to the slow zone and is a Biblical allusion to Abaddon, a place of destruction. In the Hebrew Bible, abaddon is used with reference to a dwelling place of the dead[3].

One of the book's working titles was Dandelion Sky[4], a term used in the final novel as an alternate name for the slow zone. This name would later be used for the title of the tenth episode of Season 3.